Damascene processes may be used to “build up” structures for use in a hard drive head, such as a write pole, as opposed to methods which rely upon material removal to form such 3D structures. As applied to formation of perpendicular magnetic recording (PMR) write poles, an example of which is shown in FIG. 1, the damascene process involves forming grooves or trenches in a material (e.g., Al2O3), and then depositing (e.g., electroplating) a pole material into the trenches to form write poles.
With reference to FIG. 1, convention processes used in fabrication of a PMR write pole 110 utilize a single photo/trimming process that defines two critical parameters, namely, track width (TW) 102 and nose length (NL) 104 of the write pole 110. The NL 104 is a length that a pole tip section 114 of the write pole 100 extends from an end 108 of a yoke region 112 after the nose section 114 is trimmed (e.g., by a lapping operating) to an air bearing surface (ABS) 116 of the write pole 110. The TW 102 is a width of the pole tip section 114 after the trimming. The single photo/trimming process creates a rounding of a transition region 106 where the yoke and pole tip regions 112, 114 are adjoined. A measure of the rounding is a radius of curvature (R) 104 of the transition region 106. Due to the rounding effect, it is hard to achieve a precise control of the TW 102 when a short NL 104 is required.
FIG. 2 illustrates a prior art PMR main write pole fabrication method. Although the prior art fabrication method utilizes two separate reactive ion etching (RIE) steps, transition region 206 is nevertheless defined at the first RIE etching step (left insert), and a significant rounding (e.g., R in excess of 0.4 micrometers) results from the photo and trimming processes. As a result, with such prior art fabrication methods, a short NL is coupled with a large chisel angle at ABS, and a large TW sigma ensues. Conversely, the TW sigma requirement puts a constraint on how short the NL can be.